In computing systems, such as desktop computers, portable computers, personal digital assistants (PDAs), servers, and others, storage devices are used to store data and program instructions. One type of storage device is a disk-based device, such as magnetic disk drives (e.g., floppy disk drives or hard disk drives) and optical disk drives (e.g., CD or DVD drives). Such disk-based storage devices have a rotating storage medium with a relatively large storage capacity. However, disk-based storage devices offer relatively slow read-write speeds and greater space and power consumption when compared to operating speeds of other components of a computing system, such as microprocessors and other semiconductor devices.
Another type of storage device is a solid state memory device, such as a dynamic random access memory (DRAM), static random access memory (SRAM), flash memory, and electrically erasable and programmable read-only memory (EEPROM). Although solid state memory devices offer relatively high read-write speeds, usually on the order of nanoseconds, they have relatively limited storage capacities.
With improvements in nanotechnology (technology involving microscopic moving parts), other types of storage devices are being developed. One such storage device is based on atomic force microscopy (AFM), in which one or more microscopic scanning probes are used to read and write to a storage medium. Typically, a scanning probe has a tip that is contacted to a surface of the storage medium. Storage of data in the storage medium is based on perturbations created by the tip of the probe in the surface of the storage medium. In one implementation, a perturbation is a dent or pit in the storage medium surface. The dent or pit is imprinted by heating a tip of the probe to an elevated temperature and pressing the tip against the storage medium surface.
Yet another type of storage device uses micromechanical storage cells in which each storage cell includes two deflectable cantilevers that are selectively engageable with each other at two different positions to represent different data states. Electrostatic, magnetic, or heating is used to move such deflectable cantilevers to the different positions. The different positions of the cantilevers of a storage cell cause the resistance or capacitance associated with the storage cell to change to indicate respective different data states.
The various types of storage devices discussed above may be associated with one or more of the following issues: low storage capacity, low access speed, relatively expensive manufacturing cost, circuit complexity, reduced reliability associated with having to heat storage elements during circuit operation, and others.